JP2001135490A - Discharge-lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an optimal lighting control capable of suppressing a saturation phenomenon of a transformer in a load-circuit part and improving switching actions, by enabling to control on-width so that switching actions of two switching elements may be synchronized with a simple circuit-structure. SOLUTION: A detection-circuit part 30 detects alternating power-source voltage. The detected results are added to the voltage of a smoothing capacitor C2 and given to an amplifier 16a. The amplifier 16a compares the inputted addition results with a direct-current power-source voltage Vef and gives the comparison results to an on-amplitude control part 27. Based on the comparison results, the on-width control part 27 controls a drive circuit 14 so that the on-width of a switching element Q1 which gives energy to an inductance L0 of a load-circuit part 20 may become narrow in the case where the peak value of input current becomes high and become wide inversely in the case where it becomes low. At that time, a drive circuit 15 is controlled so that another switching element Q2 may be synchronized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device capable of reducing a harmonic component of an input current by performing a combined operation of a step-up / step-down chopper operation and an inverter operation using two switching elements.

[0002]

2. Description of the Related Art In recent years, in a discharge lamp lighting device, which is an electronic ballast for a discharge lamp, in order to perform stable lighting control of the discharge lamp, a discharge lamp lighting device of various circuit types for reducing input current harmonics. Is being developed. By reducing the harmonic components included in the input current, it is possible to prevent malfunction of the device which may be caused by the influence of the harmonic components, and there is an advantage that normal lighting control can be performed.

[0003] Such a discharge lamp lighting device includes a device generally called an active filter system, and a stand-alone chopper system such as a step-up chopper type and a step-up / step-down chopper type;
There is a dual-purpose chopper type that also serves as a boost chopper element. Above all, a composite circuit configured by using a step-up / step-down chopper type or the like has attracted attention because a DC current can be obtained higher than that of a step-down type and the inrush current is not large unlike the step-up type.

FIG. 7 is a circuit diagram showing an example of such a discharge lamp lighting device.

In FIG. 7, one output terminal of an AC power supply 11 is connected via a filter 12 to one input terminal of a rectifier circuit 13, for example, a full-wave rectifier by a diode bridge, and the other output terminal is connected to the filter 12. Is connected to the other input terminal of the rectifier circuit 13. The filter 12 removes high frequency components included in the AC power supply voltage supplied from the AC power supply 11 and supplies the same to the rectifier circuit 13.
The rectifier circuit 13 performs full-wave rectification on the alternating current supplied through the filter 12 to convert the alternating current into direct current and supply the direct current to a subsequent circuit group.

[0006] Between the output terminals of the rectifier circuit 13, a capacitor C1 and first and second switching elements Q1 and Q1 are connected.
2, a step-up / step-down chopper type composite circuit composed of the smoothing capacitor C2 and the load circuit unit 20 is connected.

The first and second switching elements Q1 and Q2 are, for example, MOSFETs, and include a drain / source of the switching element Q1 and a switching element Q1.
The drain and source 2 are connected in series via a smoothing capacitor C2.

[0008] The source of the switching element Q1 is connected to the load circuit section 20, and the load circuit 20 is connected to the source of the switching element Q2 and another drive circuit 14.
The output terminal of the drive circuit 14 is connected to the gate of the switching element Q1, and the output terminal of another drive circuit 15 is connected to the gate of the switching element Q2. The drive circuits 14 and 15 generate drive signals for switching the corresponding switching elements Q1 and Q2, respectively, and drive the switching operations of the switching elements Q1 and Q2 by supplying the drive signals to the gates. The drive circuit 14
When the drive signal is generated, the drive signal is generated based on the output voltage of the switching element Q1 and the adjustment voltage from the Q1 ON width adjustment unit 17.

On the other hand, the discharge lamp lighting device is equipped with a control circuit section including the Q1 ON width adjustment section. This control circuit section is provided with a reference voltage Vef different from the DC power supply provided by the rectifier circuit 13 and the smoothing capacitor C2. The reference voltage Vef is grounded on the negative side and amplified by the amplifier 16 on the positive side.
To the input terminal on the negative electrode side. The positive-side input terminal of the amplifier 16 is connected to the positive-side base end of the smoothing capacitor C2 by a resistor R
1 and R2. A resistor R3 and a capacitor C3 are connected in series between the base end of the resistor R2 and the ground. Further, a resistor R4 for gain adjustment is connected between the negative-side input terminal and the output terminal of the amplifier 16.

In such a discharge lamp lighting device, the switching elements Q1 and Q2 alternately turn on and off under the control of the drive circuits 14 and 15. in this case,
When the switching element Q1 is turned on, energy is stored in the L component of the inductive load (load circuit unit 20). When the switching element Q1 is turned off, the energy stored in this load causes the body diode of the switching element Q2 to turn on. The voltage is stored in the smoothing capacitor C2 via the inverter and obtains a DC voltage. By such an operation, the switching elements Q1 and Q2 are alternately turned on with the obtained DC voltage as a power supply, and a high-frequency AC voltage is applied to the load circuit section 20 to turn on the discharge lamp 20a.

However, in such a conventional discharge lamp lighting device, if the switching element Q1 is used with the ON width fixed, as shown in FIG.
In the peak portion of the switch current (P1 period),
Due to the saturation state of the inductance L0 of the load circuit section 20, the switch current of the switching element Q1 increases and a switch loss occurs. Therefore, the switching element Q1 generates heat and adversely affects lighting control. There is a possibility that it will affect. FIG. 9 shows each switching element Q1, Q2 at the peak time (P1 period) of the input current shown in FIG.
The gate voltage (VGS) of Q2 and the drain current (I
Q1, IQ2) are shown. That is, as shown in FIG. 9 (c), the IQ1 flowing through the switching element Q1 has a constant ON width near the peak of the input current, so that it remains positive, and as a result, the load circuit section The inductance L0 of the output terminal 20 saturates and does not become zero level due to this, but becomes a current value as shown by a dashed line, thereby causing switch loss.

Therefore, in order to prevent this, it is necessary to change the ON width of the switching element Q1 according to the pulsating flow of the input AC voltage so that no switch loss occurs, that is, to narrow the ON width. There is a need to. In the above-described conventional device, the ON width of the switching element Q1 is controlled so as to be always kept constant.
There was a disadvantage that the harmonics of the input current could not be reduced and optimal lighting control could not be performed. When the power supply voltage fluctuates, it is necessary to compensate for the change in the lamp current accompanying the fluctuation. However, in the above-described conventional device, the ON width of the switching element Q1 is simply based on the smoothing capacitor voltage. Is determined, it is possible to obtain an optimum lamp current by changing the ON width according to the fluctuation of the power supply voltage. However, if the ON width is not modulated, there is a disadvantage that a switching loss occurs.

FIG. 10 is a circuit diagram showing another conventional discharge lamp lighting device employing a combined step-up / step-down circuit.

In FIG. 10, one output terminal of the AC power supply 11 is connected to one input terminal of a rectifier circuit 13, for example, a full-wave rectifier by a diode bridge, and the other output terminal is connected to the other input terminal of the rectifier circuit 13. Connected to.
The rectifier circuit 13 performs full-wave rectification on the alternating current supplied through the filter 12 to convert the alternating current into direct current and supply the direct current to a subsequent circuit group.

Between the output terminals of the rectifier circuit 13, a saturable C
T, ballast BC, step-up transformer L which is an insulation transformer
T and the first switching element Q1 are connected in series, and a capacitor C1 is arranged and connected. In addition, a large-capacity smoothing capacitor C2 is connected to the output terminal on the positive electrode side of the rectifier circuit 13, and the other connection end of the smoothing capacitor C2 is connected to the drain of the second switching element Q2. The source of the second switching element Q2 is connected to the gate of the second switching element Q2 via the drain of the first switching element Q1 and the secondary winding of another insulating transformer L10.

The first and second switching elements Q1 and Q2 are, for example, MOSFETs, and include a drain / source of the switching element Q1 and a switching element Q1.
The drain and source 2 are connected in series. The drain of the first switching element Q1 is connected to the gate of the first switching element Q1 and the negative output terminal of the rectifier circuit 13 via the secondary winding of the saturable CTL11. The connection point of these switching elements Q1 and Q2 is connected to the step-up transformer LT.

The secondary winding of the step-up transformer TL includes:
A load circuit group including the discharge lamp 21 and the capacitor C5 is connected, and the discharge lamp 21 is turned on at a high frequency by a high-frequency voltage generated by the oscillation of the step-up transformer LT.

In such a discharge lamp lighting device, the saturable C
The first and second switching elements are turned on / off alternately based on the gate voltage (drive signal) supplied through the secondary windings of TL10 and L11. When the power is turned on and the switching element Q1 is turned on, the DC current from the rectifier circuit 13 is supplied to the saturable CT, the ballast BC, and the step-up transformer L.
T flows through a signal line that passes between the drain and source of the switching element Q1.

As a result, energy is stored in the ballast capacitor BC and the inductor of the step-up transformer LT,
When the saturable CT is saturated, the switching element Q1 turns on. When the switching element Q1 turns on, the smoothing capacitor C2 is charged via the body diode of the switching element Q2. At this time, a positive gate voltage is generated in the saturable CTL 10, and the saturable CTL 10 can be turned on.

Ballast capacitor BC, step-up transformer L
When the energy of T is completely charged in the smoothing capacitor C2, a current flows through the switching element Q2, the boost transformer LT, the ballast capacitor BC, and the saturable CT using the smoothing capacitor C2 as a power supply.

When the saturable CT is saturated, the switching element Q2 is turned off, and resonance starts with the ballast capacitor BC, the inductor component of the boost transformer LT, and the capacitor C1. Capacitor C1 → Saturable CT → (Step-up transformer L
T) Ballast capacitor BC.

When the voltage of the capacitor C1 rises and falls, and the voltage becomes possible to conduct the rectifier 13, a current flows from the AC power supply 11. AC power supply 11 → rectifier 11 → saturable CT → ballast capacitor BC → step-up transformer LT → switching element Q1 → rectifier 12 → AC power supply 11.

Eventually, the saturable CT is saturated, and the switching element Q1 is turned off.

Such an operation is repeatedly performed. Thus, the first and second switching elements Q1, Q2
, The current given to the discharge lamp 21 becomes a lamp current on the secondary winding side by the oscillation of the step-up transformer LT, and the discharge lamp 20a is turned on at a high frequency. In the configuration shown in FIG. Although the input current is close to a sine wave, there is a disadvantage that the peak value of the lamp current is high, that is, the ripple becomes large. In order to reduce the ripple, it is necessary to control the ON width of the first switching element Q1 to be constant.

However, in the control method in which the ON width of the first switching element Q1 is constant, when the ON width is wide as shown in FIG. 11A, the input current Iin near the zero cross of the power supply voltage becomes excessive. If a step is generated, or if the ON width is narrowed by the operation of suppressing the step generated near the zero crossing of the input current, the third harmonic component increases, which adversely affects the lighting control performance. There was an inconvenience.

[0026]

As described above, in the conventional discharge lamp lighting device, in the peak portion of the input current flowing through the switching element, the switching element Q1
If the ON width of the switching element Q1 is fixed, the current becomes excessively large, and a switching loss of the switching operation of the switching element Q1 occurs due to the saturation state of the inductance L0 of the load circuit section 20, and as a result, the lighting is performed. There is a possibility that control may be adversely affected. To prevent this, the switching element Q1
It is necessary to change the ON width of the switching element Q1 so as not to cause a switch loss. However, the ON width of the switching element Q1 is controlled to be always kept constant.
There was a disadvantage that the harmonic components of the input current could not be reduced and optimal lighting control could not be performed.

When the power supply voltage fluctuates, it is necessary to compensate for the change in the lamp current accompanying this fluctuation. However, the ON width of the switching element Q1 is determined simply based on the smoothing capacitor voltage. Therefore, the ON width can be changed according to the fluctuation of the power supply voltage, and the optimum lamp current can be obtained. However, there is a disadvantage that the switching loss cannot be reduced.

Further, in another conventional discharge lamp lighting device,
Since the ON time of the first switching element Q1 is a control method in which the ON time is constant, if the ON width is wide, the input current near the zero cross of the power supply voltage becomes excessive, causing a step, or the input current near the zero cross of this input current. When the ON width is reduced by the operation of suppressing the generated step, the third harmonic component increases, which has a disadvantage that the lighting control performance is adversely affected.

Therefore, the present invention has been made in view of the above-mentioned problem, and has a simple circuit configuration in which the ON width can be controlled so that the switching operations of the two switching elements are synchronized with each other. It is an object of the present invention to provide a discharge lamp lighting device capable of suppressing the saturation phenomenon of the discharge lamp and improving the switching operation and performing optimal lighting control.

In addition, the present invention optimizes the modulation by changing the ON width of the switching element in accordance with the fluctuation of the power supply voltage and simultaneously modulating the lamp current in order to compensate for the change of the lamp current accompanying the fluctuation of the power supply voltage. Another object of the present invention is to provide a discharge lamp lighting device capable of obtaining a high lamp current.

Further, according to the present invention, even when a saturable CT is used, the on-time of the switching element can be controlled to improve the power factor of the input current, reduce harmonic components, and reduce the lamp current. Another object of the present invention is to provide a discharge lamp lighting device capable of performing optimal lighting control at low cost by enabling the peak value to be reduced.

[0032]

According to a first aspect of the present invention, there is provided a discharge lamp lighting device comprising: an AC power supply; a rectifier circuit that converts an AC voltage from the AC power supply into a DC power supply voltage and outputs the DC power supply voltage; A first and a second switching element for switching a DC power supply voltage from a circuit; and a high-frequency power supplied to the discharge lamp by a switching operation by the second switching element, the smoothed DC voltage obtained by the switching operation by the first switching element. A first and a second drive circuits for driving on / off of the first and second switching elements; a first detection circuit for detecting a DC voltage of the smoothing circuit; and the AC power supply A second detection circuit for detecting a voltage; and comparison means for comparing detection results from the first and second detection circuits with a reference DC power supply voltage; Controlling the first and second drive circuits in accordance with the result to control on / off of the first and second switchings to control the output power. And a control circuit for controlling the corresponding drive circuit so that the ON width of the switching element is narrow when the vicinity of the peak of the AC power supply voltage value is high, and widen at zero level when it is low. Things.

According to a second aspect of the present invention, there is provided the discharge lamp lighting device according to the first aspect, wherein the comparing means adds the second detection circuit to a detection result from the first detection circuit. The comparison between the sum of the detection results from and the reference DC power supply voltage, the control circuit,
According to the comparison result, the on-width control is performed so that the voltage of the smoothing capacitor included in the smoothing circuit becomes substantially constant.

In the first and second aspects of the present invention, the on-width of the switching element connected in series to the discharge lamp is narrowed by the control means when the vicinity of the peak of the AC power supply voltage value is high. Conversely, when the voltage is low, the corresponding drive circuit is controlled so as to be wide at zero level, so that the ON width control can be performed with a simple circuit configuration so that the switching operations of the two switching elements are synchronized. , Can suppress the saturation phenomenon of the load circuit transformer,
Switching operation can be improved. Accordingly, high-frequency power to be supplied to a good discharge lamp can be obtained, and the lighting control performance can be improved. The comparison means compares the detection result from the first detection circuit with the detection result from the second detection circuit and the reference DC power supply voltage, and performs control based on the comparison result. Since the ON width is controlled by the means, even when the power supply voltage fluctuates, the change in the lamp current due to the fluctuation can be compensated, and the ON width modulation can be easily performed.

According to a third aspect of the present invention, there is provided a discharge lamp lighting device according to the first aspect, wherein the control means is configured to control any one of the first and second switching elements. When the ON width is controlled to be fixed, the ON width is controlled by changing the ON width of the other switching element so that the voltage of the smoothing capacitor included in the smoothing circuit is substantially constant. It is assumed that.

According to the third aspect of the present invention, the same operation and effect can be obtained as in the first and second aspects of the present invention, and a good switching operation can be secured by the on-width control by the control means. The open-circuit voltage is at the end of the lamp, and the normal lamp can be controlled to be substantially constant at the secondary voltage that can be maintained for lighting. Therefore, it is possible to avoid problems at the end of the lamp without providing a special lamp life detecting circuit or the like.

According to a fourth aspect of the present invention, there is provided a discharge lamp lighting device, comprising: an AC power supply; a rectifier circuit for converting an AC voltage from the AC power supply to a DC power supply voltage and outputting the DC power supply voltage; A first and a second switching element for switching between the first and second switching elements; a high-frequency power obtained by a switching operation by the first and the second switching element is led to a primary winding, and a lamp current is supplied from the secondary winding to the discharge lamp. A load circuit including a transformer to be supplied; an inductance circuit connected to a primary side of the transformer; a second capacitor including a smoothing capacitor and a resonance capacitor, the DC voltage obtained by a switching operation of the first switching element being supplied to a second circuit. A circuit to be provided to the discharge lamp by the switching element; and a circuit for driving on / off of the first and second switching elements. And a second drive circuit; controlling the first and second drive circuits to control on / off of the first and second switching, thereby enabling control of the output power. Then, an on-width is obtained such that an on-time near a power supply voltage zero level of a switching element connected in series to the load circuit is equal to a half of a resonance cycle of the resonance capacitor, the inductance circuit, and the load circuit. And a control circuit for controlling the driving circuit corresponding to the above.

According to a fourth aspect of the present invention, the on-time of the switching element connected in series to the load circuit near the power supply voltage zero level is determined by the resonance capacitor, the inductance circuit, and the load circuit. Since the corresponding drive circuit is controlled to obtain an ON width that is the same time as half the resonance cycle, it is possible to improve the power factor of the input current, reduce harmonic components, and reduce the peak value of the lamp current Thus, optimal lighting control can be performed at low cost.

According to a fifth aspect of the present invention, in the discharge lamp lighting device according to the fourth aspect, the inductance circuit includes a saturable CT and a capacitor. Controlling the first and second drive circuits based on the saturation of the saturable CT, wherein the saturable CT is provided near the power supply voltage zero level of a switching element connected in series to the load circuit. Is controlled so as not to saturate.

According to a sixth aspect of the present invention, in the discharge lamp lighting device according to the fifth aspect, the load circuit is another saturable CT connected to the secondary side of the insulating transformer. Wherein the control means controls to change the ON width of a switching element connected in series to the load circuit based on saturation of the saturable CT in both the inductance circuit and the load circuit. It is a feature.

According to the fifth and sixth aspects of the invention, the same operations and effects as those of the fourth aspect of the invention can be obtained.
Even in a circuit configuration using a saturable CT, the ON width can be variably controlled, which contributes to an improvement in lighting control performance.

[0042]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing one embodiment of a discharge lamp lighting device according to the present invention. The device shown in FIG.
The same components as those in the apparatus shown in FIG. 7 are denoted by the same reference numerals.

In FIG. 1, one output terminal of the AC power supply 11 is connected to one input terminal of a rectifier circuit 13, for example, a full-wave rectifier using a diode bridge, via a filter 12 and a detection circuit unit 30. The other output terminal of the AC power supply 11 is connected to the other input terminal of the rectifier circuit 13 via the filter 12 and the detection circuit unit 30. The filter 12 removes high frequency components included in the AC power supply voltage supplied from the AC power supply 11 and supplies the same to the rectifier circuit 13. The rectifier circuit 13 performs full-wave rectification on the alternating current supplied through the filter 12 to convert the alternating current into direct current and supply the direct current to a subsequent circuit group.

Between the output terminals of the rectifier circuit 13, a capacitor C1 and first and second switching elements Q1, Q
2, a step-up / step-down chopper type circuit composed of the smoothing capacitor C2 and the load circuit unit 20 is connected.

The first and second switching elements Q1 and Q2 are, for example, MOSFETs, and include a drain / source of the switching element Q1 and a switching element Q1.
The drain and source 2 are connected in series via a smoothing capacitor C2.

The source of the switching element Q1 is connected to the load circuit section 20, and the load circuit section 20 is connected to the source of the switching element Q2 and another drive circuit 14. The output terminal of the drive circuit 14 is connected to the gate of the switching element Q1.
The output terminal of another drive circuit 15 is connected to this gate.

The drive circuits 14 and 15 generate drive signals for switching the corresponding switching elements Q1 and Q2, respectively, and supply the drive signals to the gates of the corresponding switching elements. , Q2. In this case, when generating the drive signal, the drive circuit 14 creates a drive signal based on the output voltage of the switching element Q1 and the adjustment voltage from the ON width adjustment unit 27, and the drive circuit 15 also generates the drive signal. The drive signal is generated based on the output voltage of the ON signal and the adjustment voltage from the ON width adjustment unit 27.

The load circuit section 20 is a circuit group including the discharge lamp 20a, and includes a transformer L1 connected between the source of the switching element Q1 and the source of the switching element Q2.
And a capacitor C4 connected in parallel with the transformer L1.
And a series circuit with a discharge lamp 20a including a transformer L2 and a capacitor C5.

On the other hand, a control circuit unit including the ON width adjusting unit 27 is mounted on the discharge lamp lighting device. This control circuit section is provided with a reference voltage Vef different from the DC power supply provided by the rectifier circuit 13 and the smoothing capacitor C2. The reference voltage Vef is grounded on the negative side and amplified by the amplifier 16 on the positive side.
a is connected to the input terminal on the negative electrode side. The positive input terminal of the amplifier 16a is connected to the positive input terminal of the smoothing capacitor C2 via the resistors R1 and R2. A resistor R3 and a capacitor C3 are connected in series between the base end of the resistor R2 and the ground. The amplifier 16
A resistor R4 for gain adjustment is connected between the negative-side input terminal and the output terminal of “a”, and the output terminal is connected to the ON width adjustment unit 27.

In the present embodiment, in order to solve the above-described problem, the detection circuit unit 30 is provided, and the control content of the ON width adjustment unit 27 in the control circuit unit is improved.

The detection circuit section 30 detects a pulsating fluctuation of the AC power supplied from the AC power supply 11 through the filter 12, and includes at least three resistors R5, R6, R
7 and one capacitor C6. Resistance R
A series circuit of the resistor 5 and the resistor R6 is connected between the positive output terminal of the filter 12 and the ground. One end of the resistor R7 is connected to the negative output terminal of the filter, and the other end of the resistor R7 is connected to the midpoint between the resistors R4 and R6 and the positive input terminal of the amplifier 16a via a capacitor C6. .

Therefore, such a connection makes it possible to detect fluctuations in the pulsating current of the AC power supply, that is, to detect the vicinity of the peak of the input current of the switching element. This detection result is supplied to the positive input terminal of the amplifier 16a. The amplifier 16a always compares the sum of the smoothing capacitor voltage generated in the smoothing capacitor C2 and the detection result from the detection circuit unit 30 with the reference potential Vef, and supplies the comparison result to the ON width adjustment unit 27. That is, the detection result from the detection circuit unit 30 can be reflected in the ON width adjustment control by the ON width adjustment unit 27.

The ON width adjusting section 27 controls the drive circuits 14 and 15 based on the comparison result from the amplifier 16a so as to change the ON width of the switching elements Q1 and Q2. Specifically, as shown in FIG. 2, on-width modulation control is performed so as to reduce the peak value near the peak of the lamp current. That is, the ON width adjustment unit 27 variably controls the ON width of the switching element Q1 so as to control the voltage of the capacitor C2, which is a smoothing power supply, substantially constant, and performs switching that applies energy to the inductance LO of the load circuit unit 20. The drive circuit 14 is controlled so that the ON width of the element Q1 is narrow when the peak value of the input current is high, and wide when the peak value of the input current is low.

When controlling the ON width of the first switching element Q1, the ON width adjusting section 27 also controls the ON width of the second switching Q1 in synchronization with the control. That is, when the discharge lamp 20a is turned on or the like, the ON width adjustment unit 27 drives and controls the drive circuits 14 and 15 so that the two switching elements Q1 and Q1 are alternately switched. The ON width is controlled so that the element Q1 and the second switching element Q2 are synchronized.

Thus, the switching loss of the switching element Q1 can be eliminated, and the switching of the switching elements Q1 and Q2 is controlled so as to suppress the current from the AC power supply so that the inductance LO of the load circuit section 20 does not become saturated. Since operation control can be performed, harmonic components included in the input current can be reduced, and as a result, an optimum lamp current can be obtained and lighting control performance can be improved.

Further, even when the input AC power supply voltage fluctuates, the fluctuation is detected by the detection circuit section 30 and the ON width of the switching element Q1 is changed and controlled based on the detection result, thereby providing an optimum control. A high lamp current can be obtained, and the lighting control performance can be improved.

Next, the operation of the apparatus shown in FIG. 1 will be described in detail with reference to FIG. In the device shown in FIG.
Under the control of the drive circuits 14 and 15, the switching elements Q1 and Q2 alternately turn on and off. In this case, when the switching element Q1 is turned on, energy is stored in the L component of the inductive load (the load circuit unit 20). When the switching element Q1 is turned off, the energy stored in this load is stored in the switching element Q2. The DC voltage is obtained by being stored in the bypass capacitor C2 via the body diode. By such an operation, the switching elements Q1 and Q2 are alternately turned on with the obtained DC voltage as a power supply, and a high-frequency AC voltage is applied to the load circuit unit 20.
The discharge lamp 20a is turned on.

In this case, when the peak value near the peak of the input current of the switching element is high, the inductance LO of the load circuit section 20 is saturated, and the switching loss of the switching Q1 occurs. At this time, a peak value near the peak of the input current is detected by the detection circuit section 20, and a voltage obtained by adding the detection result to the pulsating current of the AC power supply is supplied to the positive input terminal of the amplifier 16a. The comparison with the reference DC power supply voltage Vef is performed by 16a, and the comparison result is supplied to the ON width adjustment unit 27.

Then, the ON width adjusting section 27 recognizes that the peak value near the peak of the input current is high, and performs ON width modulation so as to reduce the peak value.
As shown in FIG. 3A, the drive circuit 14 is controlled so as to reduce the ON width of the switching element Q1. Of course,
The ON width adjustment is performed so as to synchronize the other switching elements Q2.

Then, the current IQ1 flowing through the switching element Q1 is as shown in FIG. 3C, and the current IQ2 flowing through the switching element Q2 is as shown in FIG. 3D.

When the peak value near the peak of the input current decreases, the drive circuit 14 is controlled by the on-width controller 27 so that the on-width of the switching element Q1 is increased near the zero cross.

As a result, the continuous operation of the switch current can be avoided so as to suppress the current from the AC power supply so that the inductance LO of the load circuit section 20 does not become saturated, so that the switch loss of the switching element Q1 is reduced. Can be eliminated. Therefore, the switching element Q
Since the switching operation control of Q1 and Q2 can be performed optimally, it is possible to obtain the optimal lamp current to be supplied to the load circuit section 20 by reducing the harmonic components of the input current, and to improve the lighting control performance. Becomes possible.

Therefore, in this embodiment, the saturation phenomenon of the transformer in the load circuit can be suppressed with a simple circuit configuration,
Since the ON width variable control can be performed so that the switching operations of the two switching elements are synchronized, the switching operation of the switching elements Q1 and Q2 can be improved to perform optimal lighting control. Further, the switching element detects fluctuations in the power supply voltage, adds the detection result to the voltage of the smoothing capacitor C2 serving as a smoothing power supply, and controls the smoothing capacitor voltage to be substantially constant based on the comparison result with the reference DC voltage. Is controlled so as to change the ON width of the lamp, it is possible to compensate for a change in the lamp current due to a change in the power supply voltage, and it is also possible to improve the lighting control performance.

In the above embodiment, the load circuit 20
The ON width of the switching element that stores energy in the inductance LO is variably controlled so as to be narrower at the peak with respect to the input current and wider at the zero crossing. For example, the ON width adjusting unit 27 controls at least two switching elements Q1 and Q2. When the ON width of one of the switching elements is fixed, the ON width of the other switching element may be variably controlled so that the voltage of the smoothing capacitor serving as the smoothing power supply is substantially constant. As a result, a good switching operation can be ensured, and the open-circuit voltage can be controlled to be almost constant at a secondary voltage that can maintain the lighting of the normal lamp, and a special lamp life detecting circuit or the like can be used. Even without this, there is also obtained an effect that problems at the end of the lamp life can be avoided. By the way, in the present invention,
The present invention is not limited to the discharge lamp lighting device employing the step-up / step-down chopper type composite circuit in the above embodiment, and can be applied to a lighting device employing another composite circuit. FIG. 4 shows such an embodiment.

4 to 6 show another embodiment of the discharge lamp lighting device according to the present invention, and FIG. 4 is a circuit diagram showing an example of a discharge lamp lighting device constituted by using a saturable CT. 5
Is a characteristic diagram showing an input voltage waveform and an input current waveform of the device, and FIG. 6 is a characteristic diagram showing an output current waveform obtained by on-time control by the device. In the apparatus shown in FIG. 4, the same components as those in the apparatus shown in FIG. 10 are denoted by the same reference numerals.

In FIG. 4, the discharge lamp lighting device according to the present embodiment includes a driver circuit 31 for driving the switching operation of the second switching element Q2,
The configuration is substantially the same as that of the conventional device shown in FIG. 10 except that an ON width control unit 32 for controlling the ON width (ON time) of the first and first switching elements Q1 is provided.

That is, one output terminal of the AC power supply 11 is connected to one input terminal of a rectifier circuit 13, for example, a full-wave rectifier by a diode bridge, and the other output terminal is connected to the other input terminal of the rectifier circuit 13. Is done. The rectifier circuit 13 performs full-wave rectification on the alternating current supplied through the filter 12 to convert the alternating current into direct current and supply the direct current to a subsequent circuit group.

Between the output terminals of the rectifier circuit 13, a saturable C
T, ballast BC, step-up transformer L which is an insulation transformer
T and the first switching element Q1 are connected in series, and a capacitor C1 is arranged and connected. In addition, a large-capacity smoothing capacitor C2 is connected to the output terminal on the positive electrode side of the rectifier circuit 13, and the other connection end of the smoothing capacitor C2 is connected to the drain of the second switching element Q2. The source of the second switching element Q2 is connected to the step-up transformer LT and the drain of the first switching element Q1.

The first and second switching elements Q1 and Q2 are, for example, MOSFETs, and have a drain / source of the switching element Q1 and a switching element Q1.
The drain and source 2 are connected in series. The drain of the first switching element Q1 is connected to the capacitor C1 and the negative output terminal of the rectifier circuit 13, and is connected to the gate of the first switching element Q1 via the ON width control unit 32. You. The connection point of these switching elements Q1 and Q2 is connected to the step-up transformer LT which is the insulating transformer.

The secondary winding of the step-up transformer TL includes:
A load circuit group including the discharge lamp 21, the saturable CTL 12 (which may not be provided), and the capacitor C5 is connected, and the discharge lamp 21 is turned on at a high frequency by a high frequency voltage generated by the oscillation of the step-up transformer TL.

The saturable CT, the ballast BC, and the boost transformer LT constitute a resonance circuit.

In this embodiment, in order to reduce the harmonics of the input current, the first and second switching elements Q1, Q
A driver circuit 31 and an ON width control unit 32 are provided as control means capable of controlling the ON width (ON time) of the second. In the conventional device, since the ON width of the first switching element Q1 is a control method that is not constant, when the ON width changes, the input current waveform of the switching element is disturbed as described above. Therefore, the ON time is important for determining the optimum ON width to prevent this, and is particularly desirable for a buck-boost composite circuit. Therefore, the control section including the driver circuit 31 and the ON width control section 32 controls the ON width of the first and second switching elements so that the ON time becomes a predetermined period.

For example, the ON width control unit 32 determines that the ON time near the zero cross of the current flowing through the switching element Q1 connected in series with the load circuit unit depends on the resonance cycle due to the inductance component of the resonance circuit including the inductance of the load circuit unit. The ON width is controlled so as to be half of. At the same time, the ON width control unit 32 controls the driver circuit 20 at a timing synchronized with the ON width control. This allows
The driver circuit 31 synchronizes the switching of the second switching element Q2 by supplying a drive signal having the opposite phase to the drive signal of the first switching element Q2 to the gate of the second switching element Q2 to be connected. And drive. The ON width control unit 32
Has a built-in driver circuit (not shown) for driving the first switching element Q1, and is configured to change the ON width in accordance with the change in the ON time by controlling this driver circuit. It is a thing.

Next, the operation of the apparatus shown in FIG. 4 will be described in detail with reference to FIG. In the discharge lamp lighting device having the above configuration, the first and second switching elements are turned on / off alternately based on the gate voltage (drive signal) supplied via the on-width control unit 32 and the driver circuit 31.
When the power supply is turned on and the switching element Q1 is turned on, the DC current from the rectifier circuit 13 becomes saturable CT and ballast B
C, a boost transformer LT, and a signal line flowing between the drain and source of the switching element Q1.

As a result, energy is stored in the ballast capacitor BC and the inductor of the step-up transformer LT.
When the saturable CT is saturated, the switching element Q1 turns on. When the switching element Q1 turns on, the smoothing capacitor C2 is charged via the body diode of the switching element Q2. At this time, a positive gate voltage is generated in the saturable CTL 10, and the saturable CTL 10 can be turned on.

Ballast capacitor BC, step-up transformer L
When the energy of T is completely charged in the smoothing capacitor C2, a current flows through the switching element Q2, the boost transformer LT, the ballast capacitor BC, and the saturable CT using the smoothing capacitor C2 as a power supply.

When the saturable CT is saturated, the switching element Q2 is turned off, and resonance starts with the ballast capacitor BC, the inductor component of the boost transformer LT and the capacitor C1. Capacitor C1 → Saturable CT → (Step-up transformer L
T) Ballast capacitor BC.

When the voltage of the capacitor C1 rises and falls, and the voltage becomes conductive in the rectifier 13, a current flows from the AC power supply 11. AC power supply 11 → rectifier 11 → saturable CT → ballast capacitor BC → step-up transformer LT → switching element Q1 → rectifier 12 → AC power supply 11.

Eventually, the saturable CT saturates, and the switching element Q1 turns off.

By repeating such an operation, the current supplied to the discharge lamp 21 on the secondary winding side by the oscillation of the step-up transformer LT becomes the lamp current,
The discharge lamp 20a is turned on at a high frequency.

In this case, the ON width control section 32 turns ON the current near the zero crossing of the current flowing through the switching element Q1 so that the ON time becomes half the resonance cycle due to the inductance component of the resonance circuit including the inductance of the load circuit section. Control the width. That is, at the time of resonance by the resonance circuit, a voltage (ν) waveform between the terminals of the rectifier circuit 13 having a resonance period T shown in FIG. 6A is obtained. On time is
It has a characteristic that is half of the resonance period. Of course, the switching of the second switching element Q2 is also turned on / off in synchronization with the switching operation of the first switching element by the control of the driver circuit 31 by the ON width control unit 32.

Therefore, the switching operation by the first and second switching elements Q1 and Q2 is performed in such an ON width, so that the saturable CT is not saturated and the secondary winding side of the step-up transformer LT is not saturated. It is possible to reduce the harmonics contained in the input current without any step near the zero cross, thereby obtaining the optimum lamp current and performing the high-frequency lighting of the discharge lamp 20a optimally. Becomes As a result, not only can the lighting control be improved in performance, but also it can be implemented with a simple circuit configuration, which greatly contributes to cost reduction.

Therefore, according to the present embodiment, even when the discharge lamp lighting device is constituted by a composite circuit using the saturable CT, the on-time of the switching element can be controlled, and the power factor of the input current can be controlled. It is possible to improve the operation, reduce the harmonic components, and reduce the peak value of the lamp current, thereby enabling optimal lighting control at low cost.

In the embodiment according to the present invention, a circuit configuration employing a step-up / step-down chopper type composite circuit has been described. However, the present invention is not limited to this, and the switching operation is performed by at least one switching element. The present invention can be applied to any circuit that generates a lamp current to be applied to a discharge lamp, and similar effects can be obtained.

[0086]

As described above, according to the present invention, the on-width variable control can be performed with a simple circuit configuration so that the switching operations of the two switching elements are synchronized. The saturation phenomenon can be suppressed, and the switching operation of the switching elements Q1 and Q2 can be improved to perform optimal lighting control. Further, the switching element detects fluctuations in the power supply voltage, adds the detection result to the voltage of the smoothing capacitor C2 serving as a smoothing power supply, and controls the smoothing capacitor voltage to be substantially constant based on the comparison result with the reference DC voltage. Is controlled so as to change the ON width of the lamp, it is possible to compensate for a change in the lamp current due to a change in the power supply voltage, and it is also possible to improve the lighting control performance. Furthermore, even when the discharge lamp lighting device is configured by a composite circuit using a saturable CT, the on-time of the switching element can be controlled, thereby improving the power factor of the input current, reducing the harmonic components, and improving the lamp. It is possible to reduce the peak value of the current and to perform optimal lighting control at low cost. This makes it possible to provide a high-performance discharge lamp lighting device at lower cost than before.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a discharge lamp lighting device according to the present invention.

FIG. 2 is a current waveform diagram when ON width modulation is performed.

FIG. 3 is a waveform chart for explaining the operation of the device shown in FIG. 1;

FIG. 4 is a circuit configuration diagram showing another embodiment.

FIG. 5 is a characteristic diagram showing an input voltage waveform and an input current waveform of the device.

FIG. 6 is a waveform chart showing an output current waveform obtained by on-time control by the device.

FIG. 7 is a circuit diagram showing an example of a conventional discharge lamp lighting device.

FIG. 8 is a waveform chart showing AC voltage and switch current waveforms.

FIG. 9 is an output waveform diagram for explaining a problem of the device of FIG. 7;

FIG. 10 is a circuit diagram showing an example of another conventional discharge lamp lighting device.

FIG. 11 is an output waveform diagram for explaining a problem of the device of FIG. 10;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... AC power supply, 12 ... Filter, 13 ... Rectifier circuit, 14, 15 ... Drive circuit, 16a ... Amplifier, 20 ... Load circuit part (L0), 20a ... Discharge lamp, 27 ... On width adjustment part, 30 ... Detection circuit Section, Q1: first switching element, Q2: second switching element, C2: smoothing capacitor.

Claims (6)

[Claims] An AC power supply; a rectifier circuit that converts an AC voltage from the AC power supply into a DC power supply voltage and outputs the DC power supply voltage; and first and second switching elements that switch the DC power supply voltage from the rectifier circuit. A circuit for applying high-frequency power to a discharge lamp by a switching operation of a second switching element with a smoothed DC voltage obtained by a switching operation of the first switching element; and turning on / off the first and second switching elements. Drive the first
And a second drive circuit; a first detection circuit for detecting a DC voltage of the smoothing circuit; a second detection circuit for detecting the AC power supply voltage; and detection from the first and second detection circuits. A comparison unit for comparing the result with a reference DC power supply voltage, and controlling the first and second drive circuits according to the comparison result to turn on / off the first and second switching. Controlling the output power, wherein the on-width of the first switching element is narrow when the vicinity of the peak of the AC power supply voltage value is high, and conversely at zero level when the AC power supply voltage value is low. A control circuit for controlling a corresponding drive circuit so as to be wider. 2. The control means according to claim 1, wherein said comparing means compares said detection result from said first detection circuit with a detection result from said second detection circuit and said reference DC power supply voltage. 2. The discharge lamp lighting device according to claim 1, wherein the circuit controls the ON width so that the voltage of the smoothing capacitor included in the smoothing circuit becomes substantially constant according to the comparison result. 3. 3. The control means controls the smoothing circuit with respect to the other switching element when controlling to fix the ON width of one of the first and second switching elements. The discharge lamp lighting device according to claim 1, wherein the ON width is controlled by varying the ON width so that the voltage of the included smoothing capacitor is substantially constant. 4. An AC power supply; a rectifier circuit for converting an AC voltage from the AC power supply into a DC power supply voltage and outputting the DC power supply voltage; and first and second switching elements for switching the DC power supply voltage from the rectifier circuit. A load circuit including a transformer in which high-frequency power obtained by the switching operation of the first and second switching elements is guided to a primary winding and supplies a lamp current from a secondary winding to a discharge lamp; An inductance circuit connected to the primary side; a smoothing capacitor and a resonance capacitor;
A circuit for applying a DC voltage obtained by the switching operation of the switching element to the discharge lamp by the second switching element, and first and second driving circuits for driving on / off of the first and second switching elements. Controlling on / off of the first and second switching by controlling the first and second drive circuits, thereby enabling the output power to be controlled; The corresponding drive circuit is controlled such that an on-time near the power supply voltage zero level of the switching elements connected in series is equal to a half of a resonance cycle of the resonance capacitor, the inductance circuit, and the load circuit. A discharge lamp lighting device, comprising: 5. The saturable C.
T, wherein the control means controls the first and second drive circuits based on the saturation of the saturable CT, and includes a switching circuit connected in series to the load circuit. 5. The discharge lamp lighting device according to claim 4, wherein the on-width control is performed so as not to saturate the saturable CT near the zero level of the power supply voltage of the element. 6. 6. The load circuit further includes another saturable CT connected to a secondary side of the insulating transformer, and the control unit controls the saturable CT in both the inductance circuit and the load circuit. The discharge lamp lighting device according to claim 5, wherein control is performed to change an ON width of a switching element connected in series to the load circuit based on the saturation.